Percussive rock-drill.



C. DAVENPORT.

PERCUSSIVE ROCK DRILL,

APPLICATION FILED JULY 15, 1911.

Patented Feb. 25, 191-3.

INVENTOR WITNESSES:

A TTOR/VEV CARL DAVENPORT, 0F SHEFFIELD, ENGLAND, ASSIGNOR 0 F .ONE-HAI-I TO RICHARD UNITED s'rArEs PATENT OFFICE.

NICHOLSON, OF SHEFFIELD, ENGLAND.

PEB/CUSSIVE BOOK-DRILL.

Patented Feb. 25', 1913.

Application filed July 15, 1911. Serial no. eaaeao.

To all whom it may concern Be it known that I, CARL DAVENPORT, subject of England, residing at the Aztec Works, Neepsend, Sheffield, in the county of York, England, have invented new and useful Improvements in or Relating to Percussiye Rock-Drills and the Like, of which the following is a specification.

My inventionrelates to im rovements in drills and boring tools of t e percussion type, such as are largely used. in mining operations, and the ObJGCt of my invention is to construct such drills and boring tools, (hereinafter referred to as drills), in such a manner that the bit or cutting portion can be attached to and firmly secured to a holder or drill bar and can be removed therefrom when it becomes necessary to sharpen it or substitute another hit.

I carry out my invention in the following manner the nature of which will'b'ebetter understood on reference to the accompanying sheet of drawings in which,"

Figure l, is a sectional elevation of a cutter bar, cutter and rivet pin before the parts have been secured together, Fig. 2, is a cor=' responding view after the parts have'been secured together. Fig. 3, is an enlarged sectional elevation of the rivet pin inside the screw ed holes before it has been subjected to pressure as shown in thesmaller scale Fig.1.

Fig. 4 is a plan of the top end of the rivet pin showing thecentral hole and radial cuts.

The same letters refer to similar parts throughout the several views.

In the cutter end of the drill bar, a, which has been previously set up or enlarged, I bore or otherwise form a parallel hole or recess, 6 concentric and in line with the axis of the bar, and for a short distance from the opening I form internal helical corrugations or screw threads, t. threads being, rounded both at their periphery and root and not V shaped like a Whitworth thread, the threads so formed being by preference right handed as shown in Figs. 1, 2 and 3. Into this partly threaded hole I accurately fit a parallel pin or rivet 0, of dead soft steel or other suitable metal, clear of the threads, and which beds trul at the bottom of the hole; a small hole, being drilled down its center and slightly countersunk. The outer end of this pm or rivet, 0, when driven or forced into position The chisel shaped or of other desired form, has

a recess, f, bored or otherwise'formed in 1ts back, such recess being slightly-undercut and provided with a coned projection, f, in its center. The outer end ofthis recess is also provided with internal helical corrugations or screw threads, t ,'of a similar pitch and formation to the threads alreadydescribed for the end of the drillbar, but in this case the threads are made left handed. Into this partly threaded hole in'the bit or cutter e, the end of the parallel pin or rivet, c, which projects from the end of the drill bar, a, is now. forced or driven. clear of the threads, so that the ta ered the small hole, (Lin the center of the pin or rivet. In this position the back of the bit or cutter, e, is some distance apart from the end of the drill bar by reason of the pin or rivet, 0, being a little longer than the distance between the bottom of the hole, 6, in the drill bar and the end of'the conedlproection, f, in the bit-{o1- c'utter when the two parts are closed together. When the two parts'are hammered or otherwise forced into position, the end ofthe rivet pin, 0, is forced or splayed, by the action of. the central projection, until it partly or completel fills up the recess, f, around the cone in t e bit or cutter and by reason of the same being un-'.

P j f at the bottom of the ho e comes in line with extra length and its soft and ductile nature,

- is forced or intruded into the threads, 6 and t which have been'formed in the hole in the bit, a, and in the hole in the (11-111 bar, b, thereby formingv right and left handed threads on the rivet pin, a, before the surfaces of the bit and the drill bar abut upon each other. I By this form of construction and by reason of the right and left handed screws, 1,, t, herein described the bit, e, may

be screwed off the rivet pin a, so as to exer cise sufficient force to draw the head a, of

the rivet pin out of thehole in the bit when it is desired to exchange the hit for another one or when it is only desired tosharpen the bit. By turning the bit, e, in'the cpposite direction the rivetpin, 0, may be un-" screwed out of the drill bar, a, with the bit 2, attached to it.

In some cases the threads in the drill bar may be made left handed and the threads in the cutter bit made right handed.

Having now particularly described and ascertained the nature of my said invention imam-at i iffeeess'formed in the back, said'recess being slightly undercut and provided with a coned Gprojection in its center, the outer end of said recess having left-handed screw threads of similar pitch and formation to those formed in the end of the drill bar, and a pin of soft material fitted in said recesses, also in said right and left handed screw threads, and in the said undercut portion formed in the recess in the back of the cutter whereby the parts are held together.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

- CARL DAVENPORT.

Witnesses;

R. ER RADFom), W. H. Bnmsro. 

